MFM data connector on ST-251-1 plugged in backwards - dead?

[kbs1]

Hello

I own an old 286 PC made by DTK, it's called 'Mini 286'. It's equipped with 1mb ram and it's made in 1989. It was laying in my closet for 6 years now. I've remembered it might be a good time to change the CMOS battery. I was too late, it has already leaked. I disasambled the whole PC, resoldered a new battery, cleaned out the corrosion and it works just fine. I gave it a perfect clean. There is not a dust particle left. I disassembled and cleaned everything, including the power supply. I've never cleaned the PC before, so now it was a good time as I had to completely disassemble it to remove the main board from the case.

Eager to get it working again, I plugged in the data cable of the ST-251-1 the other way around (on the controller side, as the disk side is keyed). Now the bios was dead (obviously since I've changed the battery). I did not remember the "hard disk type" off hand. So I googled. I found this drive should be either type 30 or type 44 on my system. It has 820 cylinders and 6 heads. 44 and 30 are the only two types that match up in my bios.

However the drive is still dead. The green led comes on a couple of times at bootup, and the drive spins up, but the system says Physical disk 0 failure. What exactly has failed and can I ever know? It was plugged in the opposite side the first ~6 bootups before I gave up with the bios settings and started looking for a problem elsewhere. That's when I've found the flipped data cable.

The drive certainly did work before (6 years ago). Could I have blown something when I reversed the connector? The drive sounds normal and healthy.

Thanks

 

[SpidersWeb]

No, I get the data connector around the wrong way all the time. It's harmless.

First thing to check is you've got the correct data/controller cables connected. Make sure all the little pins in the connectors are neatly in a row and none have been pushed-in or broken.

But failing that you will most likely need to low level format the drive. It's a pretty common procedure that is often required when shifting these drives between different controllers and when they're 20+ years old the sector information loses it's strength.

Your BIOS might have this option in it, if it doesn't I would recommend using SpeedStor 6.5 (can be found on minuszerodegrees at this page: http://minuszerodegrees.net/software/software.htm) - this will let you select the drive model from a list, perform the low level format and even do the partitioning/DOS format for you, then to top it off it'll find the closest match in your BIOS and set the Drive Type.

 

[Stone]

First, don't format it if you want the data on it. Since it's on the same controller it's not yet necessary.

Does the controller have two data cable connectors? If so, are you connected to the correct one?

Does the control cable (34 pin) have two drive connectors on it? If so, is there a twist in the cable between the two drive connectors? If there is a twist then only one position is correct for that drive and more than likely it's the one in the middle of the cable and not the one at the end (after the twist).

 

[Phil Saunders]

First, don't format it if you want the data on it. Since it's on the same controller it's not yet necessary.

Does the controller have two data cable connectors? If so, are you connected to the correct one?

Does the control cable (34 pin) have two drive connectors on it? If so, is there a twist in the cable between the two drive connectors? If there is a twist then only one position is correct for that drive and more than likely it's the one in the middle of the cable and not the one at the end (after the twist).

Yes - you read my mind :D

The twisted cable got me loads of times - it's done for the same reason as for floppy drives (but the cable is different) - which connector is correct for the drive seems to vary - I've had systems about equally split, but one, and ONLY one, connector will work.

Either way, reversing the connect won't have damaged it (assuming the drive doesn't have some electrical fault)

 

[SpidersWeb]

The twisted cable got me loads of times - it's done for the same reason as for floppy drives (but the cable is different) - which connector is correct for the drive seems to vary

You can fix that variation by setting the Drive Select correctly.
For a twisted cable setup it should be DS1 (not DS0) and the primary drive will go on the connector just after the twist.

 

[Stone]

Yes - you read my mind :D

I'm going to question who read who's mind. I posted 28 hours before you got around to it. Now, if you were mulling this over and over for ~28 hours before you actually got around to posting... then I'm definitely the mind reader.

 

[kbs1]

Thank you for all your input. I have now tried each and every possible combination of cables to connect the drive up. Unfortunately, it's still the same symptoms. I've taken a few photos of my cables, the controller and the drive connected up itself. I've also individually tested each and every possible pin on each cable using my multimeter, all measured good (there are no breaks in any of the cables).

The drive was previously connected in the middle of the cable, before the twist. I am almost sure about this. However, I've tried to connect the drive to the end of the cable, and tihs yielded the same results.

Moreover for this test, I've disconnected the floppy drives altogether, so only the hard disk is connected.

I've also taken a short videoclip to see system bootup in action. When a really wrong drive type is selected (like for example 15), the message is different, Disk 0 configuration failure.

I've tried to capture the green LED on the drive it self on the video, however now it appears it never shines up. It has shoned a cople of times after I first reassembled the computer, not it seems largely dead. Is there anything I could do to revive this drive?

Also on the controller card, I've measured all pins using my multimeter while the cable was connected to the card. All pins measured OK.

I've previously tried to connect the hard drive J5 and J3, however this did not work. I do not really understand each and every connector's purpose on the controller, maybe someone could explain that would be great

However the important thing is J4 was never used before, as it's top pins are not bent. Someone bent the pins on J1, J5 and J3 before I god the machine, and that's how it came apart. So there are not that many options to connect the drive up. However maybe I could try J4 but with what counterpart? J5?

Everything is in attachments. Thank you a lot so far.

 

[kbs1]

More photos and a youtube video: http://youtu.be/NDTU6MAzJcQ

 

[modem7]

I've previously tried to connect the hard drive J5 and J3, however this did not work. I do not really understand each and every connector's purpose on the controller, maybe someone could explain that would be great

Regarding the four connectors on your hard/floppy drive controller, that is, J3/J4/J5/J1.
They match in position and designation with a lot of Western Digital controllers:

J3 = For hard drive data cable of the second hard drive (if any second drive)
J4 = For hard drive data cable of the first hard drive
J5 = For hard drive control cable

J1 = For floppy drive cable

Floppy drive

The 34-pin twisted cable you have (first photo) is a floppy drive cable. See the photo at [here] to see the difference between a floppy twisted cable and a hard drive twisted cable.

Hard drive

Therefore, the other 34-pin cable (straight-through; no twist) that you have is the control cable for the hard drive.

So connect the hard drive up to the controller per the diagram at [here], noting that per one of the notes in the diagram, when using a straight-through control cable (as you have), set the Drive Select jumper on the hard drive to the first position.

And of course, per the diagram, ensure pin 1 to pin 1.

 

[kbs1]

Wow, it boots! What a joy! Thanks a lot! The jumper was always in position 1, I must have goofed up my assumptions that J4 was never used It probably was before I disassembled it. Now it works like a charm! Including floppy A. I don't know it's size but 1.44M seems to work, it reads and writes floppies. However floppy B now does not work. It always says not ready. I have connected A to to the first port on my floppy cable (before the twist). Floppy B is connected to the very last slot. I cannot connect floppy B to the first 'big' slot because of physical constraints. So it wasn't ever connected this way. Cable is at J1. Can both floppies be on the same cable?

Thanks!

 

[modem7]

However floppy B now does not work. It always says not ready. I have connected A to to the first port on my floppy cable (before the twist). Floppy B is connected to the very last slot. I cannot connect floppy B to the first 'big' slot because of physical constraints. So it wasn't ever connected this way. Cable is at J1. Can both floppies be on the same cable?

Most clones (most, not all) copied the way that IBM did it.
Take a look at the diagram at [here].
So twisted cable (the floppy type), DS1 set on both drives, drive at cable end (i.e. after the twist) will appear as A: , drive in middle will appear as B:

 

[kbs1]

I actually connected it this way the first time around The cables are so mangled up in a small space that I mixed it up while describing it on the forum. However the floppy still does not work. It always says 'not ready' even if I try to format it. Any other suggestions?

 

[modem7]

I actually connected it this way the first time around The cables are so mangled up in a small space that I mixed it up while describing it on the forum. However the floppy still does not work. It always says 'not ready' even if I try to format it. Any other suggestions?

Does the drive's access light come on? Do you hear the spindle turn?

Photos helped before. Perhaps some photos showing us how you have cabled up the 5.25" and 3.5" drive will help.

 

[kbs1]

Hello, finally got around to it Drives A and B do not have any jumpers on the back side (no drive select jumper).

Drive B is connected before the twist (middle of the cable) as per photos. Drive A is after the twist. Photos are a bit sketchy as there is very limited space between the drives and the power supply. The cable itself is connected into J1 on the controller card.

The B: drive 'appears' to work (LED lights up when I try to read from it) - but always says 'not ready'.

The model is YD-380B. It is high density floppy and manual is actually found on this site Does it matter what density 5.25" floppy I put in? I have only one floppy to test with. That might be a problem ;-) Any suggestions are welcome, happy holidays!

 

[modem7]

So:

* A: drive (a 1.44M drive) works but not B: drive (YD-380B, a 1.2M drive).
* B: drive LED turning on at expected times.
* B: drive accesses via DOS result in 'not ready' error message.
* Presumably, B: drive was working in the computer some time over 6 years ago (i.e. not recently adding a drive of unknown status into the equation).
* Presumably, the floppy cable was working in the computer some time over 6 years ago (i.e. not recently adding a cable of unknown status into the equation).
* 5.25" floppy disk being used is of unknown status.

Your recent hard drive issue resulted from a reassembly problem. From the photos, the floppy cable/drive 'reassembly' appears to be good. the only other factor that I can think of that is tied in some way to reassembly, is the setting up of the CMOS SETUP. Did you specify the correct floppy drive types there?

It may have been as long as 10 years ago that the B: drive was successfully used. A 'deterioration' type issue that we commonly see in not-used-in-donkey-years 5.25" floppy drives is described in the 'Deteriorated lubrication' section at [here].

Do you observe that B: drive's spindle turns at the expected times ?

If you move B: drive's head carriage to about the middle location (when power is off), when you then go to access B:, does the carriage move to the 'track 0' position (as expected)?

It looks like the YD-380B is simply a more modern version of the YD-380 (what is in my IBM AT). Odd that there are no 'drive select' jumpers/switches. But, no worry; your drive is responding to the required 'drive select' line from the controller (as evidenced by the LED turning on when expected).

Does it matter what density 5.25" floppy I put in? I have only one floppy to test with. That might be a problem

The 1.2M drive will read double density disks, such as IBM DOS 3 floppies that IBM supplied. But even though the 1.2M drive will allow you to write to double density floppies, you should not do that (without good reason). Specifics are explained at [here].
If the floppy you have is a high density one, have you tried to format it in your computer?


Where are you located? You could be my next-door neighbour (the one who swears loudly at her 286 clone ).

Acquiring a known working 1.2M drive and floppy disks is obviously of great benefit, helping your diagnosis now, and providing spares for later.